Active matrix display devices have been in widespread use. The display device includes a pixel portion and a driver circuit which controls image display in the pixel portion. Specifically, in the display device, display is performed in such a manner that image signals input to a plurality of pixels arranged in matrix in the pixel portion are controlled by the driver circuit.
In recent years, concern for the global environment has been increased and development of low-power-consumption display devices has been attracting attention. For example, a technique by which power consumption of a liquid crystal display device is reduced is disclosed in Patent Document 1. Specifically, a liquid crystal display device is disclosed in which all data signal lines are electrically separated from a data signal driver to be in a high-impedance state (also referred to as an indefinite state and a floating state) during an idle period in which all scan lines and data signal lines are in a non-selected state.    [Patent Document 1] Japanese Published Patent Application No. 2001-312253